The present invention relates to a motor using piezoelectric elements to produce rotary or linear drive force.
Electric motors have heretofore required a rotor or stator with a winding or magnet. The mechanical output of these electric motors is proportional to the magnetic flux density of said rotor and stator forming a magnetic circuit. Thus, to increase the electromechanical conversion efficiency, processing or assembing technique of high accuracy has been required.
Generally, the higher the rotative speed of the motor, the higher the efficiency. However, the loss of conversion is largely the loss caused by the winding. At low speeds, large amounts of winding are required and hence the efficiency of conversion at high speeds is as low as 1/3 or 1/5 of that at high speeds.
The same may be said of the so-called linear motor which produces not a rotary but linear motion.
The rotative speed of usual motors is 1000 rpm to 2000 rpm or more. With the linear motor as it is, the distance traveled per second is 1 m to 10 m and in most cases a speed reducer is required, with the result that the motor life is short and its price is high.
Further, the rotary or running parts have high mass and hence high moments of inertia, so that the rise and fall characteristics are bad, making pulse drive difficult. Thus, pulse drive requires a clutch mechanism, brake or other parts and an auxiliary control circuit, resulting in the lack of compactness.